/*
调用格式
 mTween(box, {
    width: {
        target: 600,
        duration: 1000,
        fx: 'linear',
        callback: function() {
            console.log('width走完了');
        }
    },
    height: {
        target: 400,
        duration: 500,
        fx: 'linear',
        callback: function() {
            console.log('height走完了');
        }
    },
    opacity: {
        target: 40,
        duration: 2000,
        fx: 'linear',
        callback: function() {
            console.log('opacity走完了');
        }
    }

}, function() {
    console.log('全都走完了');
})*/

// 兼容requestAnimationFrame
(function() {
     var lastTime = 0;
     var vendors = ['webkit', 'moz'];
     for (var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
         window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
         window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] || // Webkit中此取消方法的名字变了
             window[vendors[x] + 'CancelRequestAnimationFrame'];
     }

     if (!window.requestAnimationFrame) {
         window.requestAnimationFrame = function(callback, element) {
             var currTime = new Date().getTime();
             var timeToCall = Math.max(0, 16.7 - (currTime - lastTime));
             var id = window.setTimeout(function() {
                 callback(currTime + timeToCall);
             }, timeToCall);
             lastTime = currTime + timeToCall;
             return id;
         };
     }
     if (!window.cancelAnimationFrame) {
         window.cancelAnimationFrame = function(id) {
             clearTimeout(id);
         };
     }
 }());

function cTween(obj, attrs, callback) {
     var options = {};
     var max = 0;
     var animation;
     for (var attr in attrs) {
         options[attr] = {};

         for (var att in attrs[attr]) {
             options[attr][att] = attrs[attr][att];

         }
         if (max < options[attr].duration) {
             max = options[attr].duration
         }
         if (attr == 'opacity') {
             options[attr].begin = getStyle(obj, attr) * 100;

         } else {
             options[attr].begin = getStyle(obj, attr);

         }
         options[attr].count = options[attr].target - options[attr].begin;
     }
     var time = +new Date();
     moveFn();
     function moveFn() {
         var t = +new Date() - time;
         for (var attr in options) {
             options[attr].t = +new Date() - time;
             if (options[attr].t >= options[attr].duration) {
                 options[attr].t = options[attr].duration
             }
             if (attr == 'opacity') {
                 obj.style[attr] = Tween[options[attr].fx](options[attr].t, options[attr].begin, options[attr].count, options[attr].duration) / 100;
             } else {
                 obj.style[attr] = Tween[options[attr].fx](options[attr].t, options[attr].begin, options[attr].count, options[attr].duration) + 'px';
             }
             if (options[attr].t == options[attr].duration) {
                 options[attr].callback && options[attr].callback();
                 options[attr].callback = null;
             }
         }
         if (t >= max) {
             cancelAnimationFrame(animation);
             callback && callback(obj);
             callback = null;
         } else {

             animation = requestAnimationFrame(moveFn);
         }
     }
    function getStyle(obj, attr) {
        return parseFloat(obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj)[attr]);
    }
 }

 /*
* t : time 已过时间
* b : begin 起始值
* c : count 总的运动值
* d : duration 持续时间
*
* 曲线方程
*
* http://www.cnblogs.com/bluedream2009/archive/2010/06/19/1760909.html
* */

//Tween.linear();

var Tween = {
	linear: function (t, b, c, d){  //匀速
		return c*t/d + b;
	},
	easeIn: function(t, b, c, d){  //加速曲线
		return c*(t/=d)*t + b;
	},
	easeOut: function(t, b, c, d){  //减速曲线
		return -c *(t/=d)*(t-2) + b;
	},
	easeBoth: function(t, b, c, d){  //加速减速曲线
		if ((t/=d/2) < 1) {
			return c/2*t*t + b;
		}
		return -c/2 * ((--t)*(t-2) - 1) + b;
	},
	easeInStrong: function(t, b, c, d){  //加加速曲线
		return c*(t/=d)*t*t*t + b;
	},
	easeOutStrong: function(t, b, c, d){  //减减速曲线
		return -c * ((t=t/d-1)*t*t*t - 1) + b;
	},
	easeBothStrong: function(t, b, c, d){  //加加速减减速曲线
		if ((t/=d/2) < 1) {
			return c/2*t*t*t*t + b;
		}
		return -c/2 * ((t-=2)*t*t*t - 2) + b;
	},
	elasticIn: function(t, b, c, d, a, p){  //正弦衰减曲线（弹动渐入）
		if (t === 0) { 
			return b; 
		}
		if ( (t /= d) == 1 ) {
			return b+c; 
		}
		if (!p) {
			p=d*0.3; 
		}
		if (!a || a < Math.abs(c)) {
			a = c; 
			var s = p/4;
		} else {
			var s = p/(2*Math.PI) * Math.asin (c/a);
		}
		return -(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
	},
	elasticOut: function(t, b, c, d, a, p){    //*正弦增强曲线（弹动渐出）
		if (t === 0) {
			return b;
		}
		if ( (t /= d) == 1 ) {
			return b+c;
		}
		if (!p) {
			p=d*0.3;
		}
		if (!a || a < Math.abs(c)) {
			a = c;
			var s = p / 4;
		} else {
			var s = p/(2*Math.PI) * Math.asin (c/a);
		}
		return a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b;
	},    
	elasticBoth: function(t, b, c, d, a, p){
		if (t === 0) {
			return b;
		}
		if ( (t /= d/2) == 2 ) {
			return b+c;
		}
		if (!p) {
			p = d*(0.3*1.5);
		}
		if ( !a || a < Math.abs(c) ) {
			a = c; 
			var s = p/4;
		}
		else {
			var s = p/(2*Math.PI) * Math.asin (c/a);
		}
		if (t < 1) {
			return - 0.5*(a*Math.pow(2,10*(t-=1)) * 
					Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
		}
		return a*Math.pow(2,-10*(t-=1)) * 
				Math.sin( (t*d-s)*(2*Math.PI)/p )*0.5 + c + b;
	},
	backIn: function(t, b, c, d, s){     //回退加速（回退渐入）
		if (typeof s == 'undefined') {
		   s = 1.70158;
		}
		return c*(t/=d)*t*((s+1)*t - s) + b;
	},
	backOut: function(t, b, c, d, s){
		if (typeof s == 'undefined') {
			s = 3.70158;  //回缩的距离
		}
		return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
	}, 
	backBoth: function(t, b, c, d, s){
		if (typeof s == 'undefined') {
			s = 1.70158; 
		}
		if ((t /= d/2 ) < 1) {
			return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
		}
		return c/2*((t-=2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
	},
	bounceIn: function(t, b, c, d){    //弹球减振（弹球渐出）
		return c - Tween['bounceOut'](d-t, 0, c, d) + b;
	},       
	bounceOut: function(t, b, c, d){//*
		if ((t/=d) < (1/2.75)) {
			return c*(7.5625*t*t) + b;
		} else if (t < (2/2.75)) {
			return c*(7.5625*(t-=(1.5/2.75))*t + 0.75) + b;
		} else if (t < (2.5/2.75)) {
			return c*(7.5625*(t-=(2.25/2.75))*t + 0.9375) + b;
		}
		return c*(7.5625*(t-=(2.625/2.75))*t + 0.984375) + b;
	},      
	bounceBoth: function(t, b, c, d){
		if (t < d/2) {
			return Tween['bounceIn'](t*2, 0, c, d) * 0.5 + b;
		}
		return Tween['bounceOut'](t*2-d, 0, c, d) * 0.5 + c*0.5 + b;
	}
}